Battery drain issue after factory reset - safe rooting?

[SVW]

Hi, I wonder if anyone might be able to help.

I have an S5 that updated to Marshmallow several months ago. Since then battery drain has been an issue, and recently it has become extreme and prevents me from using my phone normally. I have to switch everything off, turn screen brightness to the lowest possible setting and can hardly use it just to make it last 10 hours. Today, using it more normally, I have had to recharge three times since morning.

After much fiddling, experimentation, installing GSAM and two factory resets, I have identified that the problem lies with the WIFI. The phone is constantly awake (solid bar) when wifi is on, even when untouched with the screen off for hours - no other functions (GPS, data, regular signal, etc.) cause the same problem.

This is still happening right now, after my most recent factory reset, since when I have reinstalled no apps. GSAM was previously identifying app usage as the culprit for over 85% of the drainage, so I can only assume it comes down to one of the pre-installed apps using the wifi constantly, maybe Google Play Services, about which I have read complaints. However, to confirm what is responsible and potentially to disable play services, I need to root the phone.

With that in mind, I wonder if anyone can give me any good advice on safely rooting my phone. The model number is SM-G901F, and baseband version is G901FXXU1CPH3. I can provide other important information as required.

Thanks in advance for your suggestions.

 

[B. Diddy]

Welcome to Android Central! Before rooting, go to Settings>Privacy>Location>Improve Accuracy​, and make sure Wi-fi Scanning is turned off.

 

[SVW]

Thanks. I did already check that and it is already turned off. To be clear, the route for me is simply settings>Location>turn on Location>Improve Accuracy and the wifi scanning option comes up in a submenu there. But it's off and GPS is off anyway when the WIFI is on and causing problems, so either way, it's not the issue.

I now need to root the phone so that I can use wakelock detector and make the necessary changes/uninstalls to systems apps etc, and I am not sure where to go or what to trust. I can find zips for SM-G901F, but then the build id tends to be different, or the file is old (developed for Kitkat or Lollipop firmware).

My specs are SM-G901F and build id/baseband version is G901FXXU1CPH3 or G901FXXU1CPHA (where shown as second half of build number). Running 6.0.1. Any ideas?

 

[SVW]

I have found a CF-Auto-Root file which is for SM-G901F on 6.0.1, but the build id is

Full specs of the download are:
OEM: samsung
Model: SM-G901F
Name: kccat6xx
Device: kccat6
Board: APQ8084
Platform: apq8084
Build ID: MMB29M.G901FXXU1CPE1
Android: 6.0.1
Size: 30 373 629
Link: Download
MD5: d54cf93ba4df0ceec425976339a40f5e
#: 88 373

Doesn't quite seem to match my phone though right?

 

[B. Diddy]

Rooting is not my forte, sorry. If you'd like, I could move this to the S5 Rooting forum for more specific answers.

 

[SVW]

OK, I've successfully rooted my phone and run wakelock detector. I have now pinned the problem down to two kernel wakelocks:
> qcom_rx_wakelock
> wlan_wow_wl

I know (and I knew already) that it was wifi related. Phone is almost constantly awake when on wifi.

So far, my browsing has turned up a handful of people with the same problem and no solutions...

Have I managed to stumble on an android problem so rare that the internet hasn't got a solution? Thought this was impossible. Any ideas...?